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99 lines
4.2 KiB
99 lines
4.2 KiB
14 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/extensions/motif/doc/walkthrough.doc:147 -->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Getting Started</title>
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<font color="#004faf">Main Classes</font></a>
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<font color="#004faf">Annotated</font></a>
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</td>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Getting Started</h1>
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[ <a href="motif-walkthrough.html">Home</a> ]
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[ <a href="motif-walkthrough-2.html">Next: Preparing to Migrate the User Interface</a> ]
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<p> <h2> Starting with <a href="qmotif.html">QMotif</a> and <a href="qapplication.html">QApplication</a>
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</h2>
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<a name="1"></a><p> To be able to use Qt, we need to create a QApplication object. The
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QApplication class controls all the event delivery and display
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management for all other Qt objects and widgets. We need to use the
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QMotif class from the <em>Qt <a href="motif-extension.html#Motif">Motif</a> Extension</em> to allow QApplication
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and the <tt>XtAppContext</tt> to coexist.
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<p> The QApplication object must be created in the <tt>main()</tt> function.
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We will need to modify <tt>todo.c</tt> to compile with a C++ compiler, so we
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rename <tt>todo.c</tt> to <tt>todo.cpp</tt>.
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<p> Next, we add the appropriate includes for the QMotif and QApplication
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classes.
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<p>
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<pre></pre>
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<p> Next, we create the QMotif and QApplication objects. We create QMotif
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with a foreign <tt>XtAppContext</tt>, and we create QApplication with a
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foreign <tt>Display</tt>.
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<p> <pre></pre>
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<p> The next change is not yet necessary, but it is included to show that
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the <em>Qt Motif Extension</em> provides a complete integration.
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Normally, a Motif based program would use the <tt>XtAppMainLoop()</tt>
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function to run the application's event loop. This is still possible,
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but since we are migrating to the Qt toolkit, we prefer to use the
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<a href="qapplication.html#exec">QApplication::exec</a>() function for running the event loop.
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<p> <pre></pre>
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<p> Since we renamed <tt>todo.c</tt> to <tt>todo.cpp</tt>, we must change the
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project file and rerun <em>qmake</em> to regenerate our <tt>Makefile</tt>. When we
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build our project, there are compile and link errors: we will fix
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these in the following section.
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<p> <h2> Migrating to C++
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</h2>
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<a name="2"></a><p> We need to convert the code in this file to proper C++ code.
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Fortunately, the changes are not too large. Most files included from
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existing C projects are not C++ compatible, so we make them compatible
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by wrapping them in an <tt>extern "C"</tt> block.
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<p>
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<p> <pre></pre>
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<p> Global C functions that are forward declared must also be wrapped into
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an <tt>extern "C"</tt> block.
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<p> <pre></pre>
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<p> The <tt>manageCB()</tt> function needs to be converted to proper C++.
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<p> <pre></pre>
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<p> And we need to fix two invalid casts. One is in the <tt>Save()</tt> function.
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<p> <pre></pre>
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<p> The other invalid cast is in the <tt>Open()</tt> function.
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<p> <pre></pre>
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<p> After these changes, the project compiles and links, and the
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application runs and operates correctly.
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<p> [ <a href="motif-walkthrough.html">Home</a> ]
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[ <a href="motif-walkthrough-2.html">Next: Preparing to Migrate the User Interface</a> ]
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<p>
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<!-- eof -->
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>Qt 3.3.8</div>
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</table></div></address></body>
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